快猫短视频

RICE, which provides more than half the daily food for one third of people
across the globe, is a key target for genetic engineers seeking to develop new
crops to feed the world鈥檚 burgeoning population. Just such a strain of
genetically modified rice, which boosts yields by a massive 35 per cent, was
unveiled this week in the Philippines at an international conference on rice
biotechnology. As an added benefit, the GM rice, which has been tested in China,
Korea and Chile, extracts as much as 30 per cent more carbon dioxide from the
atmosphere than controls, offering a way of curbing global warming.

Presenting his results鈥攚hich have yet to be published鈥攁t the
conference in Manila hosted by the International Rice Research Institute,
Maurice Ku of Washington State University in Pullman says that the bumper yields
approach targets which the IRRI say will be needed to feed the population over
the coming 20 years. 鈥淭he potential is enormous,鈥� says Paul Christou, a veteran
of rice research at the John Innes Centre in Norwich. 鈥淭his rice may have
potential provided it doesn鈥檛 make poor farmers more reliant on expensive
external inputs, such as herbicides,鈥� says Kevan Bundell of the charity
Christian Aid.

To achieve such thumping gains, Ku inserted maize genes which ramp up
photosynthesis, the process by which plants harvest the energy of sunlight to
produce sugars from water and CO₂. The new genes enable the plant to
absorb more CO₂. They also stop oxygen from blocking sugar production
and, Ku believes, might even help the plant to survive hardships such as drought
and heat.

Ku and his colleagues sought to transfer maize genes because maize, sorghum
and other related 鈥淐4 plants鈥� are more 鈥渁dvanced鈥� than plants like rice. C4
plants absorb CO₂ and store large quantities of it instantly as
four-carbon acids such as oxaloacetate, malate and aspartate.

Unfortunately for farmers, most major food crops, including rice, potatoes,
wheat and other cereals, haven鈥檛 evolved the enzymes to perform this trick.
These 鈥淐3鈥� plants rely on an inferior photosynthetic kit, which creates
three-carbon compounds first, such as phosphoglycerate. This less efficient
process means that C3 plants exhale much of the CO₂ they breathe
in.

Working with Mitsue Miyao of the National Institute of Agrobiological
Resources in Tsukuba, Japan, and Makato Matsuoka at Nagoya University, Ku
inserted one of three maize genes into rice plants. The first makes
phosphoenolpyruvate carboxylase, the enzyme which initiates photosynthesis in
maize (Nature Biotechnology, vol 17, p 76). In field trials last year,
plants containing this gene yielded up to 12 per cent more rice than
controls.

But the researchers saw yields soar by 35 per cent when they inserted the
gene for pyruvate orthophosphate dikinase, another enzyme vital for C4 plants.
Tests are under way for plants containing the third crucial gene, which codes
for nicotinamide adenine dinucleotide phosphate-dependent malic enzyme.

Plants containing either of the first two genes sucked 30 per cent more
CO₂ from the atmosphere in greenhouse tests. 鈥淚f we enhance crop
productivity by taking out more CO₂, it would reduce rising CO
₂ in the atmosphere which would otherwise cause global warming,鈥� says Ku.